In vivo histological evaluation of a novel ablative fractional resurfacing device

Abstract

Background and Objectives: A novel carbon dioxide (CO 2) laser device employing ablative fractional resurfacing was tested on human skin in vivo for the first time. Study Design/Materials and Methods: An investigational 30 W, 10.6 µm CO 2 laser system was focused to a 1/e2 spot size of 120 µm to generate an array of microscopic treatment zones (MTZ) in human forearm skin. A range of pulse energies between 5 and 40 mJ was tested and lesion dimensions were assessed histologically using hematoxylin & eosin. Wound healing of the MTZ's was assessed immediately‐, 2‐day, 7‐day, 1‐month, and 3‐month post treatment. The role of heat shock proteins was examined by immunohistochemistry. Results: The investigational CO 2 laser system created a microscopic pattern of ablative and thermal injury in human skin. The epidermis and part of the dermis demonstrated columns of thermal coagulation that surrounded tapering ablative zones lined by a thin eschar layer. Changing the pulse energy from 5 to 30 mJ resulted in a greater than threefold increase in lesion depth and twofold increase in width. Expression of heat shock protein (hsp)72 was detected as early as 2 days post‐treatment and diminished significantly by 3 months. In contrast, increased expression of hsp47 was first detected at 7 days and persisted at 3 months post‐treatment. Conclusion: The thermal effects of a novel investigational ablative CO 2 laser system utilizing fractional resurfacing were characterized in human forearm skin. We confirmed our previous ex vivo findings and show for the first time in‐vivo, that a controlled array of microscopic treatment zones of ablation and coagulation could be deposited in human skin by varying treatment pulse energy. Immunohistochemical studies of heat shock proteins revealed a persistent collagen remodeling response lasting at least 3 months. We successfully demonstrated the first in‐vivo use of ablative fractional resurfacing (AFR™) treatment on human skin. Lasers Surg. Med. 39:96–107, 2007. © 2007 Wiley‐Liss, Inc.